Field
The present disclosure relates to deposition of organic thin films, including selective deposition on a first surface of a substrate relative to a second surface. Processes are also provided for particular organic film materials, independent of selectivity.
Description of the Related Art
Organic thin films have valuable optical, thermal, electrical and mechanical properties and are widely used in the electronics, medical engineering, defense, pharmaceutical, and micro- and nanotechnology industries. Polymers in the microelectronics and photonics industries include, among other examples, photon- or electron-curable/degradable polymers for lithographic patterning; and polyimides for packaging, interlayer dielectrics and flexible circuit boards. Norrman et al., Annu. Rep. Prog. Chem., Sect. C, 2005, 101, 174-201.
Polymer thin films can be used, for example, as a starting point in semiconductor applications for amorphous carbon films or layers. Polyimide films are valuable for their thermal stability and resistance to mechanical stress and chemicals. For example, polyimide films can also be used as antireflection layers to improve pattern definition and reduce misalignment in lithography steps, as layers in multiple patterning (e.g., SDDP, SDQP), as insulating materials for interlayer dielectric materials, as the gate dielectric in all-organic thin film transistors, as passivation films in packaging applications, as mask layers in etching processes, etc. Similarly, polyamide and other organic films are valuable for their electrical properties and material properties for numerous applications. Polyamide films may be used, for example, as insulating materials for interlayer dielectric materials in integrated circuit fabrication, and the photosensitivity of polyamide through ultraviolet (UV) curing allows patterning without separate photoresist.
Polymer thin films have traditionally been fabricated through spin-coating techniques. The spin-coating method forms highly functional polymer films by coating a rotating disc with a liquid material and sintering the liquid. However, tailoring of spin-applied films is limited for several reasons. For instance, formation of uniform thin films on a substrate is difficult to control, in part because of the viscosity of the starting liquid, and it can be difficult to fill the gaps of very small features (e.g., trenches or gaps between metal lines) without void generation after curing. Also, spin-coating over high topography relative to the desired thickness of the layer can result in discontinuous and non-conformal deposition. As semiconductor chip sizes continue to shrink, thinner and higher-strength films with more tunable morphology are required.
Recently, vapor phase deposition processes such as chemical vapor deposition (CVD), vapor deposition polymerization (VDP), molecular layer deposition (MLD), and sequential deposition processes such as atomic layer deposition (ALD) and cyclical CVD have been applied to the formation of polymer thin films. In CVD, a film is deposited when reactants react on a substrate surface. Gases of one or more reactants are delivered to one or more substrates in a reaction chamber. In thermal CVD, reactant gases react with one another on a hot substrate to form thin films, with the growth rate typically influenced by the temperature and the amount of reactant supplied. In plasma enhanced CVD, one or more reactants can be activated in a remote plasma generator or in situ. CVD can be performed cyclically with intervening pauses or film treatments. In ALD, deposition is also conducted by cyclical exposure of substrates to reactants, where films are built up through self-saturating reactions between the substrate surface and vapor reactants performed in cycles. The substrate or wafer is exposed to vapor phase reactants, alternatingly and repeatedly, to form a thin film of material on the substrate. In a typical process, one reactant adsorbs in a self-limiting process on the substrate. A different, subsequently pulsed reactant reacts with the adsorbed species of the first reactant to form no more than a single molecular layer of the desired material. Thicker films are produced through repeated growth cycles until the target thickness is achieved. Plasma enhanced variants of ALD, and hybrid ALD/CVD processes (e.g., with some overlap of the substrate exposure to reactant supplies) are also known.
In many applications, for example in forming etches masks, polymer films are formed and subsequently patterned over a substrate. Typically, this patterning is achieved using photolithographic techniques. However, precise placement of the lithographic pattern is required in order to correctly align the patterned polymer film with the underlying substrate features. Often such patterning results in misaligned patterned polymer films. Further, the need for precision placement of the lithographic pattern can introduce complexities into processes where such techniques are used. A need exists for more efficient and reliable techniques for depositing polymer films and for depositing polymer films aligned to features of an underlying substrate. A similar need exists for films containing metal or metallic compounds aligned to features of an underlying substrate.